Influence of BZT Doping on Structural and Multifunctional Properties of Lead Free BNT-ST Ceramics

The structural, microstructural, dielectric, ferroelectric, and electromechanical properties of (1− x ) [0.97(Bi 0.5 Na 0.5 TiO 3 ) − 0.03(SrTiO 3 )] − x [BaZr 0.2 Ti 0.8 O 3 ] ceramics were systematically investigated to understand the effects of BaZr 0.2 Ti 0.8 O 3 (BZT) doping. X-ray diffraction and Rietveld refinement confirmed a pseudo-cubic structure at x = 0.03 and a tetragonal ( P 4 bm )-cubic ( Pm −3 m ) phase coexistence at x ≥ 0.05. Dielectric studies revealed a peak dielectric constant at x = 0.07 (∼1000 at 1 kHz), correlating with structural instability. Ferroelectric measurements showed the highest remnant polarization (∼27 μC cm −2 ) at x = 0.07, while increased doping ( x ≥ 0.09) led to ergodic relaxor behavior (reduced P r , E c ). Electromechanical response exhibited a strain enhancement from 0.12% ( x = 0.03) to 0.35% ( x = 0.11), with normalized strain ( d 33 *) increasing from 170 pm V −1 to 553 pm V −1 , attributed to enhanced electrostrictive effects. These findings establish x = 0.07 as the critical composition for optimized dielectric and ferroelectric properties, while x ≥ 0.09 demonstrates the potential for actuator applications.